Vapor generator tube bank



y 1969 c c. EICH VAPOR GENERATOR TUBE BANK Sheet Filed April 13, 1967 TO TURBINE F'IG.|

R 0 H N m VE me E C N E R A L C ATTORNEY y 1969 c. c. EICH 3,442,256

VAPOR GENERATOR TUBE BANK Sheet 3 of a Filed April 13, 1967 ATTORNEY bend of the tubes.

United States Patent O 3,442,256 VAPOR GENERATOR TUBE BANK Clarence C. Eich, Mountain Lakes, N.J., assignor to Foster Wheeler Corporation, Livingston, N.J., a corporation of New York Filed Apr. 13, 1967, Ser. No. 630,726 Int. Cl. F22d 7/00 US. Cl. 122-406 11 Claims ABSTRACT OF THE DISCLOSURE A tube bank in which pairs of vertical tubes are connected to horizontal tubes in a vapor generator. Blocking means are provided in the vertical tubes for creating a restriction to the flow which is confined to the inner surfaces in the vertical tubes.

BACKGROUND OF THE INVENTION In the construction of vapor generators the superheater and reheater tube elements generally consist of tubes which are bent a number of times to achieve the desired heat transfer surface. This generally entails bending the horizontal tubes to form 'a specific configuration, with the attendant welded ties and support lugs being required for supporting the coils. In this type of construction it is generally difficult to weld the coils, and it is also necessary to use a separate wall to support the coils and enclose the gases. This type of wall does not provide an the vertical spacing between adjacent horizontal tube elements can be varied to suit the design requirements involved, whereas when conventional tubes are used, the specific configuration is limited by the minimum radius It should also be recognized that the positioning of flow restrictions in a tube bank presents serious problems with respect tomaintaining the temperature of the tube metal at workable levels. Accordingly, if restriction to flow is achieved from an obstruction, which is positioned at random in the tubes or which diverges inwardly from the internal surfaces of the tubes, a drastic reduction in flow velocity and attendant turbulent flow would be created in the vicinity of the obstruction. Also, since the fluid passing through such an obstruction would not come into direct contact with the tube wall, the heat transfer in the tube walls proximate to the obstruction would be reduced, thereby constituting an additional factor for causing the tube metal temperature to rise. Thus, as the flow velocity and heat transfer about the blocking means decreases, the tube metal temperatures could rise to the extent that the tubes would be completely destroyed. By providing restriction to flow, wherein circulation is confined to the area surrounding the in- 3,442,256 Patented May 6, 1969 ternal tube wall, the tube temperatures can be maintained at workable lower levels.

SUMMARY OF THE INVENTION In accordance with an illustrative embodiment, demonstrating objects and features of the present invention there is provided a tube bank construction for use in a vapor generator comprising vertical tube passes and horizontal tube passes. Each horizontal tube pass is connected in fluid flow communication between a pair of the vertical tube passes. The vertical tube passes are joined together externally in side-by-side relation to form a passage for conveying hot gases. Flow restriction means are disposed in the vertical tube passes for creating a reduction in the flow volume such that the flow paths in the vertical tube passes are in proximity to the internal surfaces of the vertical tube passes.

BRIEF DESCRIPTION OF THE DRAWINGS Theabove brief description as well as further objects features, and advantages of the present invention will be more fully appreciated by referring to the following description of presently preferred, but nonetheless illustrative embodiments in accordance with the present invention, when taken in connection with the accompanying drawings, wherein:

FIG. 1 is a sectional view of a portion of a vapor generator provided with a tube bank arrangement in accordance with the present invention:

FIG. 2 is a section taken along the line of 2-2 of FIG. 1 and looking in the direction of the arrows, showing the fin wall construction of the vertical tubes which form the gas passage;

FIG. 3 is an enlarged longitudinal section of the fluid restriction means shown in FIG. 1 which are disposed between two adjacent horizontal tube passes that are relatively close together;

horizontal tube passes which are spaced apart a relatively greater distance than the tubes of FIG. 3;

FIG. 5 is a section taken along the lines of 55 of FIG. 3 or 4 and looking in the direction of the arrows, showing the internal configuration of the fluid restriction means;

FIG. 6 is a tube bank construction similar to that which isshown in FIG. 1, except that a wider horizontal tube span length is utilized together with a center wall vertical tube pass;

FIG. 7 is a sectional view showing both a reheater and superheater utilizing the tube bank construction of the instant invention;

FIG. 8 is a sectional view showing the tube bank construction'of the present invention in a counter flow arrangement;

DESCRIPTION OF THE PREFERRED EMBODIMENTS of the present invention and generally designated by the referencenumeral 12. The vapor generator includes a furnace section 14 from which hot combustion gases pass through an upward vertical gas pass 16, to a horizontal gas pass 18 and into a downward vertical gas pass 20.

Positioned in horizontal gas pass 18 is a primary superheater 22 and a secondary superheater 24 which are in fluid flow communication with each other. In vapor generator 10 shown in FIG. 1, steam is generated in the wall tubes which define the furnace section 14 and upward vertical gas pass section 16. A collection header 28 is mounted above upward vertical gas pass 16 and is connected to the furnace section wall tubes. As best seen in the schematic flow diagram of FIG. 1, the steam passes from collection header 28 into a header 30 which is connected to primary superheater 22, into a header 32 which is connected to the secondary superheater 24, and out through an outlet header 34 into the turbine which is not shown in the drawings. By referring to the downward vertical gas pass 20 of FIG. 1, it can be see that steam from the turbine enters the tube bank 12 and flows upwardly into a collection header 36 which is connected to the turbine.

Referring now to the downward vertical gas pass 20 shown in FIG. 1, it can be seen that the tube bank construction 12 in accordance with the present invention comprises pairs of vertical tube passes 40 and 42 which are connected in flow communication between horizontal tube passes 50. Each of the individual vertical tube passes 40 and 42 are connected together externally by means of fin walls 60, thereby forming walls 62 of the passage for conveying gases in downward vertical gas pass 20.

In accordance with the present invention, flow restriction means 70 are positioned within vertical tube passes 40 and 42 for reducing the volume of flow in tube bank 12 and confining the flow path to the inner surface of vertical tube passes 40 and 42. The flow restriction means 70, which are positioned adjacent to horizontal tube passes 50 that are spaced relatively close together, includes a spherical block 72 which is secured in vertical tube passes 40 and 42 by means of a backing ring 84. For fabrication purposes, it is preferable to form spherical block 72 with a hollow internal construction. The backing ring 84 is formed in the shape of an annulus having a circular inner wall 86 and circular outer wall 88. Through flow channels 90 are formed in backing ring 84, extending radially outward from inner wall 86 towards outer wall 88, and uniform flow can best be achieved by providing three of the flow channels 90 in backing ring 84 which are spaced equidistantly about the circumference of the tube pass cross-section, as shown in FIG. 5.

The flow channel 90 is defined by a lateral outer wall 92 formed in backing ring 84, a lateral inner wall 94 on the outer periphery of spherical block 72 and spacedapant radial side walls 95 formed in backing ring 84. A groove 96 is formed on the inner wall of vertical tube passes 40 and 42 for accommodating backing ring 84, such that the latter inner wall 94 is substantially coextensive with the inner wall surface of the tube passes 40 and 42. Thus, radial side walls 95 of flow channel 90 are formed with a suflicient depth to allow backing ring 84 to fit into groove 96 with the flow channel 90 diverging radially inwardly from the inner wall surface of tube passes 40 and 42 to the outer wall surfaces of the spherical block 72. Accordingly, the flow paths through channels 90 are confined to the inner wall surface area of vertical tube passes 40 and 42, such that the temperature of the tube metal can be prevented from rising above the capability of the tube metal. Thus, by maintaining the flow velocity and fluid contact with the inner wall surface of the vertical tube passes surrounding flow restriction means 70, it is possible to regulate fluid flow without causing the tube metal temperature to rise to the point of failure.

From FIG. 4, it can be seen that the flow restriction means 70 is in the form of an oblong cylindrical block 98 which can be utilized in connection with adjacent tube passes 50 which are spaced apart from each other at a substantially greater distance. -By referring to FIG. 1 and progressively inspecting spherical block 72 and cylindrical block 98, the need for flow restriction means 70 of different configurations can be readily appreciated, in order to regulate the flow between adjacent horizontal tube passes which are spaced apart varying distances from each other.

In accordance with the instant invention, the spherical blocks 72 and cylindrical blocks 98 have been inserted between lengths of vertical tubes which are welded together. Accordingly, to mount the spherical block 72 in the vertical tube passes 40 and 42, it is necessary to first insert the spherical block 72 into the backing ring 84 with the inner wall 86 contacting the exterior surface of spherical block 72. Any convenient means of mounting can be used for the spherical block 72 and backing ring 84, such as welding. Once the spherical block 72 and backing ring 84 have been joined together it is then possible to slip the free ends of the tube lengths, comprising vertical tube passes 40 and 42 together, over backing ring 84. For this purpose, groove 96 is formed on the interior surface at the free ends of the vertical tube passes 40 and 42 for accommodating backing ring 84 in order that circular welds 99 can be fabricated as best shown in FIGS. 3 and 4. Since cylindrical block 98 and spherical block 72 have identical cross-sectional hollow internal configurations, as shown in FIG. 5, the same reference numerals and description relating to flow channels and welds 99 have been used in connection with spherical block 72 and cylindrical block 98.

The cylindrical block 98 is mounted in vertical tube passes 40 and 42 in a similar manner to the mounting of the spherical block 72. In this connection, it is preferable to utilize two of the backing rings 84 thereby necessitating the formation of two circular weld-s 99. By referring to FIG. 4, it can been seen that each of the cylindrical blocks 98 is connected by means of three individual vertical tube lengths.

It should be understood that the blocking means 70 of the instant invention could also be utilized without backing ring 84. In order to eliminate the backing ring it would be necessary to fabricate the spherical block 72 and cylindrical block 98 with outer diameter dimensions substantially identical to the inner diameter dimensions of the vertical tube passes being used. Also, the through flow channels 90 would have to be formed along the outer surface extending radially inwardly on spherical block 72 and cylindrical block 98. This would require diflicult fabrication, and accordingly, the preferred embodiment utilizing the backing ring 84 has been selected for illustration in the drawings.

In FIG. 6 there is illustrated a further embodiment of the invention in which corresponding parts have been designated by the same reference numerals as part of a 100 series. In this form of the invention, a double tube bank 138 is mounted in the downward vertical gas pass 20. The double tube bank 138 includes three substantially parallel vertical tube passes 140, 142, and 144. The vertical tube passes 140 and 142 are joined together in fluid flow communication with substantially parallel and spaced apart horizontal tube passes 150. The vertical tubes 142 and 144 are joined together in flow communication by the substantially parallel and spaced apart horizontal tubes 152. Both the spherical blocks 72 and cylindrical blocks 98 can be inserted in vertical tube passes 140, 142, and 144, but for the sake of clarity only spherical block 72 has been shown in FIG. 6. The double tube bank 138 is provided for use in instances when the vertical gas pass 20 has a span of a substantially greater width which could not normally be accommodated by the single tube bank 38.

In FIG. 7, there is illustrated a still further embodiment of the invention wherein corresponding parts have been designated by the same reference numerals as part of a 200 series. In this form of the invention, there is provided a reheater and superheater tube bank 238 which is mounted in the vertical gas pass 20. The reheater and superheater tube bank 238 includes a reheater section comprising substantially parallel spaced apart vertical tubes 240 and 242 joined together in fluid flow communication by substantially parallel and spaced apart horizontal tubes 250. Similarly, the superheater section of tube bank 238 includes substantially parallel and spaced apart vertical tubes 252 and 254 joined together in fluid flow communication by the substantially parallel and spaced apart horizontal tubes 256. The spherical blocks 72 and cylindrical blocks 98 are shown in FIG. 7, inserted in vertical tube passes 240, 242, and 254.

In FIG. 8 there is illustrated a still further embodiment of the invention wherein corresponding parts have been designated by the same reference numerals, but as part of a 300 series. In this form of the invention, there is provided a counter flow tube bank 338 which includes a direct flow section 338A integrally joined to a counter flow section 338B. The counter flow section 338A includes pairs of vertical tube passes 340 and 342 which are connected in flow communication with horizontal tube passes 350. The counter flow section 338B includes pairs of vertical tube passes 352 and 354 which are connected in flow communication with horizontal tube passes 356. The vertical tube passes 340 and 352 are integrally connected by 180 degree tube bend section 360 such that the fluid in tube passes 352 flows in an opposite direction or counter to the fluid in tube passes 340. Similarly, tube passes 342 are integrally joined to tube passes 354 by 180 degree tube bend section 362 such that the fluid in tube passes 354 flows in an opposite direction or counter to the fluid in tube passes 342. The spherical blocks 72 and cylindrical blocks 98 are shown in FIG. 8, inserted in vertical tube passes 340, 342, 352, and 354.

A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed Without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein:

What is claimed is:

1. A tube bank construction for use in a vapor generator comprising vertical tube passes including cylindrical wall defining internal tube surfaces, horizontal tube passes connected in fluid flow communication between said vertical tube passes, said vertical tube passes being externally joined together in side-by-side relation to form an exterior passage for conveying hot gases, and flow restriction means in said vertical tube passes for creating a reduction in the flow volume such that the flow circulation paths in said vertical tube passes are in proximity to said internal tube surfaces, said flow restriction means including at least one spherical block and at least one annular backing ring coaxially mounted in said vertical tube passes, said spherical block being coaxially mounted in said backing ring, and said backing ring being formed with through flow channels diverging radially outwardly from said spherical block to said internal tube surface.

2. A tube bank construction for use in a vapor generator comprising vertical tube passes including cylindrical walls defining internal tube surfaces, horizontal tube passes connected in fluid flow communication between said vertical tube passes, said vertical tube passes being externally joined together in side-by-side relation to form an exterior passage for conveying hot gases, and flow restriction means in said vertical tube passes for creating a reduction in the flow volume such that the flow circulation paths in said vertical tube passes are in proximity to said internal tube surfaces, said flow restriction means including at least one cylindrical block and at least one annular backing ring coaxially'mounted in said vertical tube passes, each of the cylindrical blocksbeing coaxially mounted in each of the backing rings and said backing ring being formed with through flow channels diverging radially outwardly from said cylindrical block to said internal tube surface.

3. A double tube bank construction for use in a vapor generator having gas passages with'a relatively wide horizontal tube span, said tube bank comprising a plurality of pairs of outer vertical tube passes, each of which are spaced apart from and separated by a vertical disposed central tube pass, said vertical tube passes and central tube pass including cylindrical walls defining internal tube surface, horizontal tube passes connected in fluid flow communication between said central tube pass and each pair of said vertical tube passes, said vertical tube passes being externally joined together in side-by-side relation to form an exterior passage for conveying hot gases, and flow restriction means in said vertical tube passes and said central tube pass for creating a reduction in the flow volume such that the flow circulation paths in said vertical tube passes are in proximity to said internal tube surfaces.

4. A tube bank according to claim 3 in which said flow restriction means comprise spherical blocks having 5. A tube bank according to claim. 3 in which said flow restriction means comprise cylindrical blocks having through flow channels which diverge radially outwardly towards said internal tube surfaces such that fluid contact is contiguous with the internal tube: surfaces which surround said cylindrical blocks.

-6. A tube bank construction for use in a vapor generator comprising a plurality of pairs of reheater vertical tube passes and a plurality of pairs of superheater vertical tube passes, said vertical tube passes including cylindrical walls defining internal tube surfaces, horizontal tube passes connected in fluid flow communication between the vertical tubes of each of said pairs of reheater tube passes and the vertical tubes of each of said pairs of superheater tube passes, said vertical tube passes being externally joined together in side-by-side relation to form an exte- I 7. A tube bank according to claim 6 in which said flow restriction means comprise spherical blocks having through flow channels which diverge radially outwardly towards said internal tube surfaces such that fluid contact is contiguous with the internal tube surfaces which surround said spherical blocks.

8. A tube bank according to claim 6 in which said flow restriction means comprise cylindrical blocks having through flow channels which diverge radially outwardly towards said internal tube surfaces such that fluid contact is contiguous with the internal. tube surfaces which surround said cylindrical blocks.

9. A tube bank construction for use in a vapor generator comprising pairs of direct flow vertical tube passes, pairs of counter flow vertical tube passes connected in fluid ilow communication with said direct flow tube passes, said vertical tube passes including cylindrical walls defining internal tube surfaces, horizontal tube passes connected in fluid flow communication between the vertical tubes of each of said pairs of direct flow passes and the vertical tubes of each of said pairs of counter flow tube passes, said vertical tube passes being externally joined together in side-by-side relation to form an exterior passage for conveying hot gases, and flow restriction means in said vertical tube passes for creating a reduction in the flow volume such that the flow circulation paths in said vertical through flow channels which diverge radially outwardly towards said internal tube surfaces such that fluid contact is contiguous with the internal tube surfaces which surround said cylindrical blocks.

References Cited UNITED STATES PATENTS 1,988,659 1/1935 LaMont 122-406 XR I FOREIGN PATENTS 671,267 9/1963 Canada. 779,335 7/ 1957 Great Britain.

CHARLES J. MYHRE, Primary Examiner. 

